Method for sealing pipelines using a gel pig

ABSTRACT

The present invention provides methods and methods for curing a leakage in a pipeline, the method including at least one gel pig and at least one sealant composition; wherein the at least one gel pig and the at least one sealant composition form a pig train, adapted to move along the pipeline to a region of the leakage and to seal the leakage.

FIELD OF THE INVENTION

The present invention relates generally to gel pigs for use in pipelines and methods for producing them, and more specifically to methods and apparatus for use in water pipelines.

BACKGROUND OF THE INVENTION

Many liquids are transported via subterranean/underwater pipelines. When a leakage crack or hole forms in the pipeline, the liquid leaks therefrom. Often, it takes a long time to detect a leakage and yet longer to locate the leakage site. Oil, gas and water transportation are thus subject to tremendous losses due to pipeline leakage.

There is thus a need to maintain and seal subterranean/underwater pipelines quickly in situ.

Several patent publications in the field include U.S. Pat. No. 3,523,826A which relates to a process for cleaning a piping system which is characterized by circulating in, and through said system a thixotropic emulsion having a hi.-h volume ratio of internal phase to external phase, the emulsion having an emulsifying agent, an emulsifiable oil and a non-oil, the emulsion being an oil-in-non-oil or a non-oil-in-oil emulsion, the internal phase of said emulsion being present in said emulsion in an amount of at least 80% by volume of the emulsion, said emulsion having the characteristics of a solid when at rest and the characteristics of a liquid when a force is exerted on it, said emulsion tending to be non-adhesive, said emulsion having a critical shear point sufficient to permit pumping at high rates, and said emulsion having an apparent rest viscosity greater than about 1000 cps.

U.S. Pat. No. 4,216,026 describes a method for removing fluid and/or particulate debris from a pipeline, a Bingham plastic fluid plug is passed through a pipeline and the fluid and/or debris are collected by the plug. The plug is pushed through the pipeline with a scraper which in turn may be pushed by liquid or gas pressure. Where the fluid to be removed is water, the Bingham plastic fluid plug employed preferably is a composition of water and a xanthan gum, and the gum may be cross-linked with a multivalent metal. Where the fluid to be removed is a hydrocarbon, the Bingham plastic fluid plug employed preferably is a composition of a mineral oil and an organo-modified smectite, and may also include a particulate filler such as powdered coal.

U.S. Pat. No. 4,252,465A describes a gel plug, which is employed during construction of an offshore pipeline to separate a gas-filled portion of the pipeline from a water-flooded portion, and to facilitate control and movement of the gas/gel plug/water interface as desired to assist in construction operations.

U.S. Pat. No. 4,254,559A relates to an interior surface of a pipeline being dried by sequentially passing through the pipeline (a) an aqueous cross-linked gelled pig, (b) a fluid mobility buffer comprising a non-cross-linked gelled ankanol of from one to three carbon atoms, (c) a dessicating amount of a liquid alkanol from one to three carbon atoms. For example, a pipeline was dried by sequentially passing through it (a) a borate cross-linked hydroxypropyl guar gum pig, (b) a fluid mobility buffer comprising methanol thickened with hydroxypropyl cellulose, and (c) methanol.

U.S. Pat. No. 4,379,722 discloses a gel plug of mineral oil, organo-modified smectite, and a particulate filler such as powdered coal, or a gel plug of mineral oil and organo-modified smectite is employed during construction of an off-shore pipeline to separate a gas-filled portion of the pipeline from a water-flooded portion, and to facilitate control and movement of a gas/gel plug/water interface as desired to assist in construction operations.

U.S. Pat. No. 4,416,703 describes a method to remove particulate debris from a pipeline, a plug train including at least one gel plug having debris entraining characteristics and at least one pseudoplastic plug is passed through a pipeline and the debris is collected by the gel plug. The gel plug is pushed through the pipeline with a scraper which in turn may be pushed by liquid or gas pressure.

U.S. Pat. No. 4,321,968A discloses gelled compositions comprising carboxymethylhydroxyethyl cellulose in aqueous brine solutions, which are gelled by the addition of an alkaline earth metal hydroxide such as calcium hydroxide. The gelled compositions have utility as water diversion agents, pusher fluids, fracturing fluids, drilling muds, work-over fluids, and completion fluids.

U.S. Pat. No. 5,346,339A provides a method of cleaning a pipeline using a gel pig of a graft copolymer of a hydroxyalkyl cellulose prepared by a redox reaction with vinyl phosphonic acid. The gel pig is formed by hydrating the graft copolymer in an aqueous liquid. The gel pig is crosslinked by the addition of a Lewis base or Bronsted-Lowry base, to the gel in an amount sufficient to initiate crosslinking of the graft copolymer. Contaminants entrained in the crosslinked gel pig during the cleaning process may be separated by the addition of a pH reducing agent to the pig whereby the viscosity of the gel is caused to decrease. The gel may be used for further cleaning after contaminant separation by addition of an additional quantity of the Lewis base or Bronsted-Lowry base.

US2003109385A provides a process for treating a hydrocarbon-bearing formation having at least one hydrocarbon bearing zone and at least one water bearing zone wherein the ratio of the permeability of the hydrocarbon bearing zone(s) to the permeability of the water bearing zone(s) is in the range of from 1:20 to 3:1 comprising: a) sequentially injecting into the formation: (i) an aqueous polymer solution comprising 0.01 to 0.5 weight percent of a water-soluble polymer having from 0.01 to 7.5 mole percent of crosslinkable carboxylate and/or phosphonate groups and a molecular weight in the range of 250,000 to 12,000,000; and (ii) an aqueous solution of a crosslinking agent; and b) back-producing the aqueous polymer solution over the crosslinking agent so that the polymer crosslinks within the formation to form a gel which is collapsible to allow hydrocarbon flow.

US2008277112A discloses a method for treating a portion of a subterranean formation or a propellant pack is provided. In general, the method comprises the steps of: (A) forming or providing a treatment fluid comprising: (i) water; (ii) a chelating agent capable of forming a heterocyclic ring that contains a metal ion attached to at least two nonmetal ions; and (iii) a viscosity-increasing agent; and (B) introducing the treatment fluid into the wellbore under sufficient pressure to force the treatment fluid into the matrix of the formation or the propellant pack.

WO2008081441 describes a method of repairing leakage in pipelines comprising the steps of forming a first and second openings in the pipeline upstream and downstream, respectively, of the leakage location, inserting through the first opening a first body, filling the space arrear of the first body (C1) with a first viscous sealing material (M1), inserting through the first opening a second body (C2) arrear of the first viscous sealing material (M1) compressing the first sealing material by applying a pressure against the first and the second bodies (C1, C2) in opposite directions, causing the first and second bodies (C1, C2) and the compressed first sealing material (M1) to move in unison in the direction of the second opening, and retrieving the first and second bodies (C1, C2). Preferably, the method is performed using three bodies (C1, C2, C3) and two sealing materials (M1, M2).

However, there are still many types of pipeline leakages, which cannot be cured using the aforementioned prior art materials and methods. There thus remains an urgent need to develop systems and methods for curing pipeline leakages.

SUMMARY OF THE INVENTION

It is an object of some aspects of the present invention to provide methods of forming gel pigs for use in systems and methods for sealing pipeline leakages.

In preferred embodiments of the present invention, improved methods are provided for producing gel pigs.

In other embodiments of the present invention, a method and system are provided for sealing leaks in water transport pipelines.

There is thus provided according to an embodiment of the present invention, a method for curing at one leakage site in a pipeline, the method including

-   -   a. introducing a pig train into the pipeline, the pig train         including;         -   i) at least one gel pig; and         -   ii) at least one sealant composition; wherein the at least             one gel pig and the at least one sealant composition form             said pig train;     -   b. enabling the pig train to move along the pipeline to a region         of the at least one leakage and to seal the at least one         leakage.

Additionally, according to an embodiment of the present invention, the at least one gel pig includes one gel pig and the at least one sealant composition includes one sealant composition.

Moreover, according to an embodiment of the present invention, the at least one gel pig includes two gel pigs and the at least one sealant composition includes one sealant composition.

Further, according to an embodiment of the present invention, the at least one gel pig includes three gel pigs and the at least one sealant composition includes two sealant compositions.

Yet further, according to an embodiment of the present invention, the pig train moves along the pipeline at a speed of 0.01 to 10 m/s.

Furthermore, according to an embodiment of the present invention, the at least one gel pig includes one rear pig.

Additionally, according to an embodiment of the present invention, at least one of the two pigs has an average diameter of at least 5% less than an internal diameter of the pipeline.

Moreover, according to an embodiment of the present invention, at least one of the two pigs has an average diameter of at least 10% less than an internal diameter of the pipeline.

Importantly, according to an embodiment of the present invention, the at least one gel pig includes;

-   -   a. a cellulosic polysaccharide;     -   b. a surfactant; and     -   c. water.

Additionally, according to an embodiment of the present invention, the at least one gel pig further includes;

-   -   d. a filler; and     -   e. a metallic hydroxide.

According to another embodiment of the present invention, the at least one gel pig further includes an oil.

Moreover, according to an embodiment of the present invention, the at least one gel pig includes a rear pig and a front pig of different compositions.

Furthermore, according to an embodiment of the present invention, wherein the pig train conforms to an inner profile of the pipeline.

Additionally, according to an embodiment of the present invention, the inner profile of the pipeline is reduced in diameter in at least one section by at least 20%.

Further, according to an embodiment of the present invention, the inner profile of the pipeline is reduced in diameter in at least one section by at least 50%.

Yet further, according to an embodiment of the present invention, the inner profile of the pipeline is reduced in diameter in at least one section by at least 75%.

Additionally, according to an embodiment of the present invention, the inner profile of the pipeline is further increased in the diameter in at least one section by at least 20%.

Moreover, according to an embodiment of the present invention, the inner profile of the pipeline is increased in the diameter in at least one section by at least 50%.

Additionally, according to an embodiment of the present invention, the inner profile of the pipeline is increased in the diameter in at least one section by at least 75%.

Furthermore, according to an embodiment of the present invention, the method further includes propelling a pressurized fluid from a first end thereof along the pipeline.

Additionally, according to an embodiment of the present invention, the pressurized fluid includes a liquid.

Moreover, according to an embodiment of the present invention, the pressurized fluid includes a gas.

Further, according to an embodiment of the present invention, he pressurized fluid includes a tri-phase fluid.

Yet further, according to an embodiment of the present invention, the pressurized fluid is at a pressure of 1-150 bar.

Additionally, according to an embodiment of the present invention, the pig train prevents a bypass of a propelling product by of more than 30%.

Moreover, according to an embodiment of the present invention, the method further includes extracting the pig train from the pipeline via a conduit of less than two inch diameter at a pressure of less than 3 bar.

Furthermore, according to an embodiment of the present invention, the method further includes introducing or launching the pig train into the pipeline via a conduit of less than two inch diameter at a pressure of less than 5 bars.

Additionally, according to an embodiment of the present invention, the method further includes counter-pressurizing the pig train from a second end of the pipeline with a counter pressurized fluid.

Further, according to an embodiment of the present invention, the counter pressurized fluid is for controlling velocity of movement of the pig train along the pipeline.

Yet further, according to an embodiment of the present invention, the pig train is launched from a pipe of a diameter of less than 75% of the pipeline.

Additionally, according to an embodiment of the present invention, the pig train is launched from a pipe of a diameter of less than 50% of the pipeline.

In some cases, according to an embodiment of the present invention the pig train is launched from a pipe of a diameter of less than 75% of the pipeline.

Additionally, according to an embodiment of the present invention, the pig train is launched from a pipe at an angle of greater than 30° to the pipeline.

Furthermore, according to an embodiment of the present invention, the pig train is launched from a pipe at an angle of greater than 60° to the pipeline.

In some cases, according to an embodiment of the present invention, the pig train is launched from a pipe at an angle of greater than 80° to the pipeline.

Additionally, according to an embodiment of the present invention, the pig train is launched from a pipe at a pressure in the range of 2-15 bar.

Further, according to an embodiment of the present invention, the pig train is launched from a pipe at a pressure in the range of 2-5 bar.

Importantly, according to an embodiment of the present invention, the pig train travels through an obstruction in the pipeline and is operative thereafter.

Additionally, according to an embodiment of the present invention, the obstruction is selected from the group consisting of a butterfly valve, a wedge, a nail, a screw, an obstructing element, an in-pipe meter, a service pipe ferrule, an incrustation and a tuberculation, a baffle, a broomstick seal and combinations thereof.

The present invention provides systems and methods for curing a leakage in a pipeline, the system including at least one gel pig and at least one sealant composition; wherein the at least one gel pig and the at least one sealant composition form a pig train, adapted to move along the pipeline to a region of the leakage and to seal the leakage.

The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings:

FIG. 1A is a simplified pictorial illustration showing a system for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 1B is a simplified pictorial illustration showing another system for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 1C is a simplified pictorial illustration showing another system for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 1D is a simplified pictorial illustration showing another system for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 2 is a simplified flow chart of a method for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 3 is a simplified flow chart of another method for sealing a pipeline, in accordance with an embodiment of the present invention;

FIG. 4 is a simplified flow chart of another method for sealing a pipeline, in accordance with an embodiment of the present invention; and

FIG. 5 is a simplified pictorial illustration showing a system for sealing a pipeline, in accordance with an embodiment of the present invention.

In all the figures similar reference numerals identify similar parts.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that these are specific embodiments and that the present invention may be practiced also in different ways that embody the characterizing features of the invention as described and claimed herein.

Reference is now made to FIG. 1A, which is a simplified pictorial illustration showing a system 100 for sealing a pipeline, in accordance with an embodiment of the present invention.

System 100 is constructed and configured to seal a pipeline 106 comprising at least one leakage site 108, such as a crack or hole. System 100 comprises a sealant composition 102 and a gel pig 104. System 100 is adapted to travel along the pipeline using a first pressure force 110 to the rear of the gel pig and a counter force 112 upstream (lesser than force 110). Some non-limiting examples of the gel pig compositions appear in the examples hereinbelow. Some non-limiting examples of the sealant compositions are disclosed in Israel Patent No. 180474.

A non-limiting example of composition 104 is:

-   -   a) At least one organic or inorganic filler selected from carbon         ash, aluminum hydroxide, calcium carbonate, calcium hydroxide,         magnesium hydroxide, magnesium carbonate, titanium hydroxide,         silica, similar fillers and combinations thereof in a weight         ratio of 0.01-3% wt/wt.     -   b) At least one gelling agent selected from carrageenan, agar         agar, hydroxymethylcelluose, hydroxyethyl cellulose,         hydroxypropyl cellulose and combinations thereof in a weight         ratio of 0 to 20% wt/wt.     -   c) A coloring agent selected from a water soluble dye, a water         insoluble dye, a paint, an oxide, a metal oxide and combinations         thereof in a weight ratio of 0 to 1% wt/wt.     -   d) At least one surfactant selected from an ionic surfactant, an         anionic surfactant, a detergent, an edible oil, an inedible oil         and combinations thereof in a weight ratio of 0.01 to 10% wt/wt.     -   e) At least one aqueous agent selected from sea water, tap         water, distilled water, ice and combinations thereof in a weight         ratio of 20 to 90% wt/wt.

FIG. 1B shows a simplified pictorial illustration showing another system 120 for sealing a pipeline, in accordance with an embodiment of the present invention. System 120 comprises two gel pigs 104, 106. These gel pigs may be of identical or different compositions. These are termed herein a rear gel pig 104 and a front gel pig 106. Dispersed between the two gel pigs is sealant composition 102. Some non-limiting examples of the gel pig compositions appear in the examples hereinbelow. Some non-limiting examples of the sealant compositions are disclosed in Israel Patent No. 180474.

There can be seen in FIG. 1C a simplified pictorial illustration showing another system 140 for sealing a pipeline, in accordance with an embodiment of the present invention. System 140 comprises three gel pigs 104, 114, 118 and two sealant compositions 102, 116. These gel pigs may be of identical or different compositions. Likewise, sealant compositions 102, 116 may be identical or different. Some non-limiting examples of the gel pig compositions appear in the examples hereinbelow. Some non-limiting examples of the sealant compositions are disclosed in Israel Patent No. 180474.

A non-limiting example of composition 114 is:

-   -   a) At least one organic or inorganic filler selected from carbon         ash, aluminum hydroxide, calcium carbonate, calcium hydroxide,         magnesium hydroxide, magnesium carbonate, titanium hydroxide,         silica, similar fillers and combinations thereof in a weight         ratio of 0.01-10% wt/wt.     -   b) At least one gelling agent selected from carrageenan, agar         agar, hydroxymethylcelluose, hydroxyethyl cellulose,         hydroxypropyl cellulose and combinations thereof in a weight         ratio of 0 to 30% wt/wt.     -   c) A coloring agent selected from a water soluble dye, a water         insoluble dye, a paint, an oxide, a metal oxide and combinations         thereof in a weight ratio of 0 to 1% wt/wt.     -   d) At least one surfactant selected from an ionic surfactant, an         anionic surfactant, a detergent, an edible oil, an inedible oil         and combinations thereof in a weight ratio of 0.01 to 20% wt/wt.     -   e) At least one aqueous agent selected from sea water, tap         water, distilled water, ice and combinations thereof in a weight         ratio of 20 to 85% wt/wt.

A non-limiting example of composition 118 is:

-   -   a) At least one organic or inorganic filler selected from carbon         ash, aluminum hydroxide, calcium carbonate, calcium hydroxide,         magnesium hydroxide, magnesium carbonate, titanium hydroxide,         silica, similar fillers and combinations thereof in a weight         ratio of 0.01-10% wt/wt.     -   b) At least one gelling agent selected from carrageenan, agar         agar, hydroxymethylcelluose, hydroxyethyl cellulose,         hydroxypropyl cellulose and combinations thereof in a weight         ratio of 0 to 30% wt/wt.     -   c) A coloring agent selected from a water soluble dye, a water         insoluble dye, a paint, an oxide, a metal oxide and combinations         thereof in a weight ratio of 0 to 1% wt/wt.     -   d) At least one surfactant selected from an ionic surfactant, an         anionic surfactant, a detergent, an edible oil, an inedible oil         and combinations thereof in a weight ratio of 0.01 to 20% wt/wt.     -   e) At least one aqueous agent selected from sea water, tap         water, distilled water, ice and combinations thereof in a weight         ratio of 20 to 85% wt/wt.

FIG. 1D is a simplified pictorial illustration showing another method 160 for sealing a pipeline, in accordance with an embodiment of the present invention. Method 160 comprises two gel pigs 114, 170 and a sealant composition 102 or 116 disposed therebetween. The front gel pig 114 may be similar or identical to those described herein. The rear gel pig 170 comprises at least two or three different compositions 122, 124, 126, for introduction into a pipeline sequentially (first 122, then 124 and thereafter 126).

Additionally or alternatively, the rear gel pig comprises four compositions, five compositions, six compositions, seven compositions, eight compositions or another multiplicity of compositions. A fourth composition 128 (not shown), a fifth composition 130 (not shown), a sixth composition 132 (not shown).

Additionally or alternatively, the rear gel pig comprises four compositions, five compositions, six compositions, seven compositions, eight compositions or another multiplicity of compositions. A fourth composition 128 (not shown), a fifth composition 130 (not shown), a sixth composition 132 (not shown).

When six compositions are applied, the first composition (front to back) serves as a separator between the sealing composition and the second composition. It has a density of 1.0-1.5 g/cm³. The second composition, together with the third composition, forms a two (horizontal) layer sealant body preventing or minimizing bypass of the liquid propellant. The second composition has a density of 0.9-1.5 g/cm³ and the third composition has a density of 0.8-1.2 g/cm³. The fourth and fifth compositions isolate the third composition from the liquid propellant. Respective densities are 1.0-1.8 g/cm³ and 0.8-1.2 g/cm³. The sixth composition is a gel sealant, whose purpose is to temporarily seal the pig train from the rear upon launch. It has a density of 0.8-1.2 g/cm³.

Reference is now made to FIG. 2, which is a simplified flow chart of a method 200 for sealing a pipeline, in accordance with an embodiment of the present invention, with reference to FIG. 1A. A sealant composition, such as sealant composition 102 is introduced to pipeline 106 in a sealant composition introducing step 202. This may be performed from one end of the pipe, from a fire hydrant, from a manhole, vertical, lateral pipe, communication pipe or branch pipe.

Thereafter, gel pig 104 is introduced from the same end of the pipe as the sealant composition or from a manhole or vertical, in a gel pig composition introducing step 202.

The combination of the sealant composition 102 and gel pig 104 is termed herein a “pig train”. The pig train travels along the pipe in a travelling step 206 to site 108 of the leakage. The sealant composition is operative to seal the leakage in a sealing step 208. It typically takes a few minutes to several hours until the seal is fully cured.

Typically, gel pig 104 or any of the other gel pigs described herein is of approximately the same diameter as the inner diameter of the pipe and is typically 0.5-10 diameters in length. The physical properties of the gel pig appear in Table 4.

Reference is now made to FIG. 3, which is a simplified flow chart of another method 300 for sealing a pipeline, in accordance with an embodiment of the present invention, with reference to FIG. 1.

A first gel pig 114 is introduced to the pipe from a fire hydrant, from a manhole, vertical, lateral pipe, communication pipe or from a branch pipe in an introducing pig step 302.

A sealant composition, such as sealant composition 102 is introduced to pipeline 106 in a sealant composition introducing step 304. This may be performed from one end of the pipe or from a manhole or vertical.

Thereafter, a second gel pig 104 is introduced from the same end of the pipe as the sealant composition or from a manhole or vertical, in a second gel pig composition introducing step 306.

The combination of the sealants composition 102 and gel pigs 114, 104 or any of the other gel pigs described herein, is termed herein a “pig train”. The pig train travels along the pipe in a travelling step 308 to site 108 of the leakage. The sealant composition is operative to seal the leakage in a sealing step 310. It typically takes a few minutes to several hours until the seal is fully cured.

Typically, gel pigs 104, 114 are of approximately the same diameter as the inner diameter of the pipe and is typically 0.5-10 diameters in length. The physical properties of the front gel pig 114 appear in Table 5.

The pig train is typically recovered from the pipeline in an exit pipe step 312.

FIG. 4 is a simplified flow chart of another method 400 for sealing a pipeline, in accordance with an embodiment of the present invention, with reference to FIG. 1C.

A first gel pig 118 is introduced to the pipe from a fire hydrant, from a manhole, vertical, lateral pipe, communication pipe or from a branch pipe in a first introducing pig step 402.

A sealant composition, such as sealant composition 116 is introduced to pipeline 106 in a first sealant composition introducing step 404. This may be performed from one end of the pipe or from a manhole or vertical.

Thereafter, a second gel pig 114 is introduced from the same end of the pipe as the first sealant composition or from a manhole or vertical, in a second gel pig composition introducing step 406.

A second sealant composition, such as sealant composition 102 is introduced to pipeline 106 in a second sealant composition introducing step 408. This may be performed from one end of the pipe or from a manhole or vertical.

Thereafter, a third gel pig 104 is introduced from the same end of the pipe as the first and second sealant composition or from a manhole or vertical, in a third gel pig composition introducing step 410.

The combination of the sealants compositions 102, 116 and gel pigs 118, 114 and 104 is termed herein a “pig train”. The pig train travels along the pipe in a travelling step 412 to site 108 of the leakage. The sealant composition(s) is/are operative to seal the leakage in a sealing step 414. It typically takes a few minutes to several hours until the seal is fully cured.

Typically, gel pigs 104, 114, 118 are of approximately the same diameter as the inner diameter of the pipe and is typically 0.5-10 diameters in length. The physical properties of the front/middle gel pig 118/114 appear in Table 5.

The pig train is typically recovered from the pipeline in an exit pipe step 416. In some cases, one or more of the gel pigs may be replaced with a polymer pig, such as polyurethane.

Reference is now made to FIG. 5, which is a simplified pictorial illustration showing a system 500 for sealing a pipeline, in accordance with an embodiment of the present invention.

System 500 comprises a front gel pig 114 and a real gel pig 104. A sealant composition 102 is disposed between pigs 114 and 104, forming a pig train 120. A fluid 502 is inserted to a pipeline 501 and a first pressure P₁ 506 is applied to fluid 502. Additionally a second counter-pressure P₂, 508 is applied to a second fluid 504. Typically P₁ is greater than P₂. The average velocity of pig train 120 is determined by the fluid properties, the smoothness of the pipe interior and a pressure difference (P₁-P₂).

Pressure P1 is introduced by a pump 512, pressure from an existing network or any other suitable pressure introducing means, known in the art. The pressure P1 is typically regulated by control means, as are known in the art.

Pressure P2 may be introduced by any suitable passive means, such as a pressure relief valve 514, a discharge valve, a pressure regulator or the like.

The gel pigs of the present invention provide the following advantages:—

-   -   1) Gel pigs are adapted to multi-dimensioned pipes-adaption to         variable and changing diameters in situ.     -   2) Non-abrasive very non-abrasive (in contrast to poly pigs,         which may get stuck in a pipeline, induce a reddening of water,         induce a change of pH of the water, or may abrade tubicles).     -   3) Gel pigs of the present invention are to introduce into pipe         and to remove from pips providing system flexibility.     -   4) Gel pigs of the present invention do not normally get stuck         in the pipe (better than polymer (solid) pigs) and due to their         fluidity, can always be flushed out.     -   5) The rear pig does not compromise/dislodge/disengage newly         formed seals, in contrast to solid pigs.     -   6) Gel pigs of the present invention are fully flushable (in         contrast solid pigs leave debris).     -   7) A front pig of the present invention allows water to bypass         and overtake-allows escape route to prevent/minimize sealant         composition dilution.     -   8) In a two pig system, the rear pig acts differently to the         front pig.     -   9) Pig receiver/retriever for solid pigs is not required for gel         pigs.     -   10) The gel pigs of the present invention are biodegradable.     -   11) Gel pigs of the present invention require reduced         transportation costs—here can be formulated at/near the site of         use. Saving on transport costs.

EXAMPLES Example 1

A gel pig is formed according to the following method.

-   -   1) Chemical constituents were obtained in accordance with table         1.     -   2) A gel pig mixture was made by mixing the components of table         1 in a stirred vessel for several (1-30) minutes at ambient         temperature and pressure.     -   3) The resultant gel formed was stored in a closed container in         the dark for 0-60 days at room temperature before use.

TABLE 1 Chemical composition of gel pig Functional Example Component Constituent Weight percent [%] Hygroscopic Cellulose, gum,  1-10 component gelatin or other surfactant Oil or other 0-8 Base Aluminum  0-20 hydroxide Particulate Silica 0-2 Carrier fluid Water 70-95 Total 100

According to some embodiments, the physical properties of the gel pigs appear as in tables 2 and/or 3.

According to one or more embodiments, hydrophobic solvents are liquid oils originating from vegetable, marine or animal sources. The canola oil exemplified may be replaced by any suitable liquid oil including saturated, unsaturated or polyunsaturated oils. By way of example, the unsaturated oil may be olive oil, corn oil, soybean oil, cottonseed oil, coconut oil, sesame oil, sunflower oil, borage seed oil, syzigium aromaticum oil, hempseed oil, herring oil, cod-liver oil, canola oil, salmon oil, flaxseed oil, wheat germ oil, evening primrose oils or mixtures thereof, in any proportion.

According to one or more embodiments, the silica exemplified may be replaced by a) microsponges, b) silica, c) mineral bodies like zeolite, bentonite, (iii) graphite, including polymers, dendrimers and liposomes, or mixtures thereof, in any proportion.

According to one or more embodiments, the aluminum hydroxide exemplified may be replaced by minerals such as aluminum phosphate and calcium phosphate or mixtures thereof, in any proportion.

According to one or more embodiments, the hydroxyethyl cellulose exemplified may be replaced by any at least one polymeric additive selected from the group consisting of polysaccharides, natural polysaccharides, derivatives thereof, modified polysaccharides, derivatives thereof, starch, dextrin, glycogen, cellulose and chitin, glycosaminoglycans (GAG's), chondroitin sulphate, dermatan sulphate, keratan sulphate, heparan sulphate, heparin, and hyaluronan, amylose and amylopectin, cellulose derivatives, xanthan gum, sodium CMC, methylcellulose, and hydroxyl propyl methyl cellulose or mixtures thereof, in any proportion.

Specific non limiting examples of surfactants are an ionic surfactant, a non-ionic surfactant, a hydrophobic surfactant or mixtures thereof, in any proportion.

Exemplary hygroscopic agents that can be used in accordance with one or more embodiments include, for example, naturally-occurring polymeric materials, such as locust bean gum, sodium alginate, sodium caseinate, egg albumin, gelatin agar, carrageenan gum, sodium alginate, xanthan gum, quince seed extract, tragacanth gum, guar gum, starch, chemically modified starches and the like, semi-synthetic polymeric materials such as cellulose ethers (e.g. hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxy propylmethyl cellulose), guar gum, hydroxypropyl guar gum, soluble starch, cationic celluloses, cationic guars, and the like, and synthetic polymeric materials, such as carboxyvinyl polymers, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid polymers, polymethacrylic acid polymers, polyvinyl acetate polymers, polyvinyl chloride polymers, polyvinylidene chloride polymers and the like. Mixtures of the above compounds are contemplated.

According to some further embodiments, a base may be selected from sodium hydroxide, magnesium hydroxide, aluminum hydroxide, potassium hydroxide and combinations thereof.

TABLE 2 Physical and Chemical properties of rear gel pig minimum maximum Viscosity cPs 5 10000 Density g/cm³ 0.8 1.2

TABLE 3 Physical and Chemical properties of front gel pig minimum maximum Viscosity cPs 5 10000 Density g/cm³ 0.8 1.5

The references cited herein teach many principles that are applicable to the present invention. Therefore the full contents of these publications are incorporated by reference herein where appropriate for teachings of additional or alternative details, features and/or technical background.

It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims. 

1. A method for curing at one leakage site in a pipeline, the method comprising a. introducing a pig train into the pipeline, the pig train comprising: i) at least one gel pig; and ii) at least one sealant composition; wherein said at least one gel pig and said at least one sealant composition form said pig train; b. enabling said pig train to move along said pipeline to a region of said at least one leakage and to seal said at least one leakage.
 2. A method according to claim 1, wherein said at least one gel pig comprises one gel pig and said at least one sealant composition comprises one sealant composition.
 3. A method according to claim 1, wherein said at least one gel pig comprises two gel pigs and said at least one sealant composition comprises one sealant composition.
 4. A method according to claim 1, wherein said at least one gel pig comprises three gel pigs and said at least one sealant composition comprises two sealant compositions.
 5. A method according to claim 1, wherein said pig train moves along said pipeline at a speed of 0.01 to 10 m/s.
 6. A method according to claim 2, wherein said at least one gel pig comprises one rear pig.
 7. A method according to claim 4, wherein at least one of said two pigs has an average diameter of at least 5% less than an internal diameter of said pipeline.
 8. A method according to claim 4, wherein at least one of said two pigs has an average diameter of at least 10% less than an internal diameter of said pipeline.
 9. A method according to claim 1, wherein said at least one gel pig comprises: a. a cellulosic polysaccharide; b. a surfactant; and c. water.
 10. A method according to claim 9, wherein said at least one gel pig further comprises: d. a filler; and e. a metallic hydroxide.
 11. A method according to claim 9, wherein said at least gel pig further comprises an oil.
 12. A method according to claim 1, wherein said at least one gel pig comprises a rear pig and a front pig of different compositions.
 13. (canceled)
 14. A method according to claim 12, wherein said inner profile of said pipeline is reduced in diameter in at least one section by at least 20%. 15.-19. (canceled)
 20. A method according to claim 1, further comprising propelling a pressurized fluid from a first end thereof along said pipeline. 21.-23. (canceled)
 24. A method according to claim 14, wherein said pressurized fluid is at a pressure of 1-150 bar.
 25. A method according to claim 15, wherein said pig train prevents a bypass of a propelling product by of more than 30%.
 26. A method according to claim 1, further comprising extracting said pig train from said pipeline via a conduit of less than two inch diameter at a pressure of less than 3 bar.
 27. A method according to claim 14, further comprising counter-pressurizing said pig train from a second end of said pipeline with a counter pressurized fluid.
 28. A method according to claim 18, wherein said counter pressurized fluid is for controlling velocity of movement of said pig train along said pipeline.
 29. A method according to claim 1, wherein said pig train is launched from a pipe of a diameter of less than 50% of said pipeline. 30.-39. (canceled) 